Method for receiving ACK(acknowledgement)/NACK (negative ACK) information and method for transmitting same, user equipment and base station

ABSTRACT

The present invention relates to a wireless communication system. More particularly, the present invention, when cells each operating in different TDD DL-UL configurations are merged, provides a plan for setting a downlink ACK/NACK transmission/reception timing for a cross-CC scheduling. In addition, the present invention, according to the downlink ACK/NACK transmission/reception timing, provides a base station for transmitting a ACK/NACK channel to a user equipment, and a user equipment for receiving the ACK/NACK channel from the base station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2012/001755, filed on Mar. 9, 2012,which claims the benefit of U.S. Provisional Application Ser. Nos.61/451,598, filed on Mar. 11, 2011, 61/451,597, filed on Mar. 11, 2011,61/454,575, filed on Mar. 21, 2011, and 61/454,576, filed on Mar. 21,2011, the contents of which are all hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system.Particularly, the present invention relates a method and apparatus fortransmitting/receiving an ACK/NACK signal and a method and apparatus fortransmitting/receiving a uplink (UL) grant for UL data scheduling.

BACKGROUND ART

A general wireless communication system transmits/receives data throughone downlink (DL) band and through one uplink (UL) band corresponding tothe DL band (in case of Frequency Division Duplex (FDD) mode), ordivides a prescribed radio frame into UL time unit(s) and DL timeunit(s) in a time domain and transmits/receives data through the UL/DLtime unit(s) (in case of Time Division Duplex (TDD) mode). A BaseStation (BS) and a User Equipment (UE) transmit and receive data and/orcontrol information scheduled on a prescribed time unit basis, i.e. on asubframe basis. The data is transmitted and received through a dataregion configured in a UL/DL subframe and the control information istransmitted and received through a control region configured in theUL/DL subframe. To this end, various physical channels carrying radiosignals are formed in the UL/DL subframe.

Meanwhile, to use a wider frequency band in a recent wirelesscommunication system, introduction of carrier aggregation (or bandwidthaggregation) technology that uses a wider UL/DL bandwidth by aggregatinga plurality of UL/DL frequency blocks has been discussed.

FIG. 1 illustrates an example of performing communication in amulticarrier situation.

A multicarrier system or Carrier Aggregation (CA) system refers to asystem using a wide bandwidth by aggregating a plurality of carrierseach having a narrower bandwidth than the target bandwidth. The CAsystem is different from an Orthogonal Frequency Division Multiplexing(OFDM) system in that DL or UL communication is performed using aplurality of carrier frequencies, whereas the OFDM system up-converts abase frequency band, which is divided into a plurality of orthogonalsubcarriers, into a single carrier frequency to perform DL or ULcommunication. When a plurality of carriers each having a narrowerbandwidth than a target bandwidth is aggregated, the bandwidth of eachof the aggregated carriers may be limited to a bandwidth used in alegacy system in order to ensure backward compatibility with the legacysystem. For example, the legacy system supports bandwidths of 1.4, 3, 5,10, 15, and 20 MHz and the LTE-Advanced (LTE-A) system evolved from theLTE system may support a bandwidth wider than 20 MHz using onlybandwidths supported in the LTE system. Alternatively, CA may besupported by defining a new bandwidth irrespective of the bandwidthsused in the legacy system. The term multicarrier is used interchangeablywith the term Carrier Aggregation (CA) or bandwidth aggregation.Contiguous CA and non-contiguous CA are collectively referred to as CA.For reference, when only one Component Carrier (CC) is used forcommunication in TDD or when only one UL CC and one DL CC are used forcommunication in FDD, this

DISCLOSURE Technical Problem

In multicarrier aggregation in which a plurality of aggregated carriersis used for communication between a BS and a UE, a communication methodusing a single carrier cannot be applied to communication using multiplecarriers. A new communication method suitable for communication using aplurality of carriers while minimizing an effect on a legacy systemshould be defined.

It will be appreciated by persons skilled in the art that that thetechnical objects that can be achieved through the present invention arenot limited to what has been particularly described hereinabove andother technical objects of the present invention will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present invention, provided herein is a method forreceiving ACKnowledgement (ACK)/Negative ACK (NACK) information from abase station at a user equipment in which a plurality of cells isconfigured, including transmitting uplink data channel to the basestation in an uplink (UL) subframe U₂ of a second cell among theplurality of cells and receiving a downlink (DL) ACK/NACK channelcarrying an ACK/NACK for the UL data channel from the base station in aDL subframe D₁ of a first cell among the plurality of cells, wherein thefirst cell and the second cell have different Time Division Duplex (TDD)DL-UL configurations, the DL subframe D₁ is a subframe configured fortransmission of a DL ACK/NACK channel for a UL subframe U₁ of the firstcell (where D₁, U₁, and U₂ are non-negative integers), and the ULsubframe U₁ is a first UL subframe among the UL subframe U₂ and ULsubframes on the first cell after the UL subframe U₂.

In another aspect of the present invention, provided herein is a methodfor transmitting ACKnowledgement (ACK)/Negative ACK (NACK) informationat a base station to a user equipment in which a plurality of cells isconfigured, including receiving uplink data channel from the userequipment in an uplink (UL) subframe U₂ of a second cell among theplurality of cells and transmitting a downlink (DL) ACK/NACK channelcarrying an ACK/NACK for the UL data channel to the user equipment in aDL subframe D₁ of a first cell among the plurality of cells, wherein thefirst cell and the second cell have different Time Division Duplex (TDD)DL-UL configurations, the DL subframe D₁ is a subframe configured fortransmission of a DL ACK/NACK channel for a UL subframe U₁ of the firstcell (where D₁, U₁, and U₂ are non-negative integers), and the ULsubframe U₁ is a first UL subframe among the UL subframe U₂ and ULsubframes on the first cell after the UL subframe U₂.

In another aspect of the present invention, provided herein is a userequipment, in which a plurality of cells is configured, for receivingACKnowledgement (ACK)/Negative ACK (NACK) information from a basestation, including a Radio Frequency (RF) unit configured to transmitand receive a radio signal and a processor configured to control the RFunit, wherein the processor controls the RF unit to transmit uplink datachannel to the base station in an uplink (UL) subframe U₂ of a secondcell among the plurality of cells and controls the RF unit to receive adownlink (DL) ACK/NACK channel carrying an ACK/NACK for the UL datachannel from the base station in a DL subframe D₁ of a first cell amongthe plurality of cells, the first cell and the second cell havedifferent Time Division Duplex (TDD) DL-UL configurations, the DLsubframe D₁ is a subframe configured for transmission of a DL ACK/NACKchannel for a UL subframe U₁ of the first cell (where D₁, U₁, and U₂ arenon-negative integers), and the UL subframe U₁ is a first UL subframeamong the UL subframe U₂ and UL subframes on the first cell after the ULsubframe U₂.

In another aspect of the present invention, provided herein is a basestation for transmitting ACKnowledgement (ACK)/Negative ACK (HACK)information to a user equipment in which a plurality of cells isconfigured, including a Radio Frequency (RF) unit configured to transmitand receive a radio signal and a processor configured to control the RFunit, wherein the processor controls the RF unit to receive uplink datachannel from the user equipment in an uplink (UL) subframe U₂ of asecond cell among the plurality of cells and controls the RF unit totransmit a downlink (DL) ACK/NACK channel carrying an ACK/NACK for theUL data channel to the user equipment in a DL subframe D₁ of a firstcell among the plurality of cells, the first cell and the second cellhave different Time Division Duplex (TDD) DL-UL configurations, the DLsubframe D₁ is a subframe configured for transmission of a DL ACK/NACKchannel for a UL subframe U₁ of the first cell (where D₁, U₁, and U₂ arenon-negative integers), and the UL subframe U₁ is a first UL subframeamong the UL subframe U₂ and UL subframes on the first cell after the ULsubframe U₂.

In each aspect of the present invention, the UL subframe U₁ of the firstcell may be a first UL subframe among subframes after the UL subframe U₂of the second cell when a subframe of the first cell corresponding tothe UL subframe U₂ of the second cell operates as DL, and the ULsubframe U₁ of the first cell may be a subframe sharing the same timeresource as the UL subframe U₂ when the subframe of the first cellcorresponding to the UL subframe U₂ of the second cell operates as UL.

In each aspect of the present invention, DL ACK/NACK channels for N ULsubframes of the second cell may be transmitted from the base station tothe user equipment, in DL subframes of the first cell, which areconfigured for transmission of DL ACK/NACK channels for first M ULsubframes of the first cell among the UL subframe U₂ and subframes afterthe UL subframe U₂, wherein M and N are positive integers, and N is thenumber of consecutive UL subframes of the second cell, and M≦N.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

Advantageous Effects

According to the present invention, more effectivetransmission/reception of scheduling information for UL data can beperformed in a situation in which a plurality of carriers is aggregatedand a cross-carrier scheduling is configured between the aggregatedcarriers.

In addition, according to the present invention, more effectivetransmission/reception of ACKnowledgement (ACK)/Negative ACK (NACK) forUL data can be performed in a situation in which a plurality of carriersis aggregated and cross-carrier scheduling is configured between theaggregated carriers.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates an example of performing communication in amulticarrier situation;

FIG. 2 illustrates an exemplary structure of a radio frame used in awireless communication system;

FIG. 3 illustrates an exemplary structure of a DL/UL slot in a wirelesscommunication system;

FIG. 4 illustrates an exemplary structure of a DL subframe used in a3GPP LTE(-A) system;

FIG. 5 illustrates exemplary DL scheduling when a plurality of carriersis aggregated;

FIG. 6 illustrates an exemplary UL grant timing for PUSCH transmissionin a UU SF;

FIG. 7 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 1 of the present invention;

FIG. 8 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 2 of the present invention;

FIG. 9 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 3 of the present invention;

FIG. 10 illustrates an exemplary PHICH timing for PUSCH transmission ina UU SF;

FIG. 11 illustrates a PHICH timing for PUSCH transmission in a DU SFaccording to Method 4 of the present invention;

FIG. 12 illustrates an exemplary PHICH timing for PUSCH transmission ina DU SF according to Method 5 of the present invention;

FIG. 13 illustrates an exemplary PHICH timing for PUSCH transmission ina DU SF according to Method 6 of the present invention;

FIG. 14 illustrates an exemplary UL grant timing and a PHICH timing forPUSCH transmission in a DL SF according to the present invention; and

FIG. 15 is a block diagram illustrating elements of a BS 10 and a UE 20by which the present invention is performed.

MODE FOR INVENTION

Hereinafter, the exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is to beunderstood that the detailed description, which will be disclosed alongwith the accompanying drawings, is intended to describe the exemplaryembodiments of the present invention, and is not intended to describe aunique embodiment through which the present invention can be carriedout. The following detailed description includes detailed matters toprovide full understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention can becarried out without the detailed matters.

In some cases, to prevent the concept of the present invention frombecoming ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. In addition, whereverpossible, the same reference numbers will be used throughout thedrawings and the specification to refer to the same or like parts.

In the present invention, a User Equipment (UE) may be a fixed or mobiledevice. Examples of the UE include various devices that transmit andreceive user data and/or various kinds of control information to andfrom a base station. The UE may be referred to as a Terminal Equipment(TE), a Mobile Station (MS), a Mobile Terminal (MT), a User Terminal(UT), a Subscriber Station (SS), a wireless device, a Personal DigitalAssistant (PDA), a wireless modem, or a handheld device. In addition, inthe present invention, a Base Station (BS) means a fixed station thatperforms communication with a UE and/or another BS, and exchangesvarious kinds of data and control information with the UE and anotherBS. The BS may be referred to as an Advanced Base Station (ABS), aNode-B (NB), an Evolved-NodeB (eNB), a Base Transceiver System (BTS), anAccess Point (AP), or a Processing Server (PS).

In the present invention, a Physical Downlink Control Channel (PDCCH), aPhysical Control Format Indicator Channel (PCFICH), a Physical Hybridautomatic retransmit request Indicator Channel (PHICH), and a PhysicalDownlink Shared CHannel (PDSCH) may indicate a set of time-frequencyresources or Resource Elements (REs) carrying Downlink ControlInformation (DCI), a set of time-frequency resources or REs carryingControl Format Indicator (CFI), a set of time-frequency resources or REscarrying downlink ACK/NACK, and a set of time-frequency resources or REscarrying DL data, respectively. In addition, a Physical Uplink ControlCHannel (PUCCH), a Physical Uplink Shared CHannel (PUSCH), and aPhysical Random Access CHannel) (PRACH) may indicate a set oftime-frequency resources or REs carrying Uplink Control Information(UCI), a set of time-frequency resources or REs carrying UL data, and aset of time-frequency resources REs carrying a random access signal,respectively. In the present invention, a time-frequency resource or REthat is assigned to or belongs toPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH may be calledPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. Therefore, in thepresent invention, PUCCH/PUSCH/PRACH transmission of a UE may beconceptually identical to UL control information/UL data/random accesssignal transmission on PUSCH/PUCCH/PRACH, respectively. In addition,PDCCH/PCFICH/PHICH/PDSCH transmission of a BS may be conceptuallyidentical to DL data/control information transmission onPDCCH/PCFICH/PHICH/PDSCH, respectively.

FIG. 2 illustrates an exemplary structure of a radio frame used in awireless communication system.

Referring to FIG. 2, a 3GPP LTE(-A) radio frame is 10ms (307,200 T_(s))in duration. The radio frame is divided into 10 subframes of equal size.Subframe numbers may be assigned to the 10 subframes within the radioframe, respectively. T_(s) denotes sampling time, whereT_(s)=1/(2048×15kHz). Each subframe is 1ms long and further divided intotwo slots. 20 slots are sequentially numbered from 0 to 19 in a radioframe. Duration of each slot is 0.5ms. A time interval in which onesubframe is transmitted is defined as a Transmission Time Interval(TTI). Time resources may be distinguished by a radio frame number (orradio frame index), a subframe number (or subframe index), a slot number(or slot index), and the like.

A radio frame may have different configurations according to duplexmode. In FDD mode for example, since DL transmission and UL transmissionare discriminated according to frequency, a radio frame for a specificfrequency band includes either DL subframes or UL subframes. In TDDmode, since DL transmission and UL transmission are discriminatedaccording to time, a radio frame for a specific frequency band includesboth DL subframes and UL subframes.

Particularly, FIG. 2 illustrates a TDD frame structure used in 3GPPLTE(-A). Table 1 shows exemplary DL-UL configurations for subframes in aradio frame in TDD mode.

TABLE 1 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In Table 1, D is a DL subframe, U is a UL subframe, and S is a specialsubframe. The special subframe includes three fields, i.e., DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). DwPTS is a time period reserved for DL transmission and UpPTSis a time period reserved for UL transmission. Table 2 shows anexemplary special frame configuration.

TABLE 2 Extended cyclic prefix Normal cyclic prefix in downlink indownlink UpPTS UpPTS Normal Extended Normal Extended cyclic cycliccyclic cyclic Special subframe prefix in prefix in prefix in prefix inconfiguration DwPTS uplink uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL/UL slot in a wirelesscommunication system. Specifically, FIG. 3 illustrates the structure ofa resource grid in a 3GPP LTE(-A) system.

Referring to FIG. 3, a slot includes a plurality of OFDM symbols in thetime domain and a plurality of Resource Blocks (RBs) in the frequencydomain. An OFDM symbol may refer to one symbol duration. An RB includesa plurality of subcarriers in the frequency domain. An OFDM symbol mayalso be called an SC-FDM symbol etc. according to a multiple accessscheme. The number of OFDM symbols per slot may vary depending onchannel bandwidth and CP length. For instance, one slot includes 7 OFDMsymbols in case of a normal CP, whereas one slot includes 6 OFDM symbolsin case of an extended CP. While a subframe is shown in FIG. 2 as havinga slot with 7 OFDM symbols for convenience of description, embodimentsof the present invention are also applicable to subframes with any othernumber of OFDM symbols. A resource including one OFDM symbol and onesubcarrier is referred to as a Resource Element (RE) or a tone.

Referring to FIG. 3, a signal transmitted in each slot may be expressedby a resource grid including N^(DL/UL) _(RB)·N^(RB) _(sc) subcarriersand N^(DL/UL) _(synth) OFDM or SC-FDM symbols. N^(DL) _(RB) representsthe number of RBs in a DL slot and N^(UL) _(RB) represents the number ofRBs in a UL slot. N^(DL) _(RB) and N^(UL) _(RB) depend on a DLtransmission bandwidth and a UL transmission bandwidth, respectively.Each OFDM symbol includes N^(DL/UL) _(RB)·N^(RB) _(sc) subcarriers. Thenumber of subcarriers per carrier is determined by the size of FastFourier Transform (FFT). Subcarriers may be divided into datasubcarriers for data transmission, reference signal subcarriers forreference signal transmission, and null subcarriers for a guard band anda Direct Current (DC) component. The null carriers for the DC componentare unused remaining subcarriers and are mapped to a carrier frequencyf₀ in a process of generating an OFDM signal. The carrier frequency isalso referred to as a center frequency. N^(DL) _(symb) represents thenumber of OFDM or SC-FDMA symbols in the DL slot and N^(UL) _(symb)represents the number of OFDM or SC-FDMA symbols in the UL slot. N^(RB)_(sc) represents the number of subcarriers in one RB. An RB is definedas N^(DL/UL) _(symb) (e.g. 7) consecutive OFDM symbols or SC-FDMAsymbols in the time domain and N^(RB) _(sc) (e.g. 12) consecutivesubcarriers in the frequency domain. Therefore, one PRB includesN^(DL/UL) _(symb)·N^(RB) _(sc) REs. Each RE in the resource grid may beuniquely identified by an index pair (k,l) in a slot. k is afrequency-domain index ranging from 0 to N^(DL/UL) _(RB)·N^(RB) _(sc)−1and l is a time-domain index ranging from 0 to N^(DL/UL) _(symb)−1.

FIG. 4 illustrates an exemplary structure of a DL subframe used in a3GPP LTE(-A) system.

Referring to FIG. 4, a DL subframe may be divided into a control regionand a data region. The control region includes one or more OFDM symbols,starting from the first OFDM symbol. In the DL subframe of the 3GPPLTE(-A) system, the control region is configured as a region in which aPDCCH can be transmitted. Accordingly, the control region in the DLsubframe is also referred to as a PDCCH region. The number of OFDMsymbols used for the control region in the DL a subframe may beindependently configured on a subframe basis and signaled through aPCFICH. A BS may transmit control information to a UE or UEs in thecontrol region. To transmit control information, a PDCCH, a PCFICH, aPHICH, etc. may be allocated to the control region.

The BS may transmit information related to resource assignment of aPaging CHannel (PCH) and a DL Shared CHannel (DL-SCH) that are transportchannels, a UL scheduling grant (hereinafter, UL grant), a DL schedulinggrant (hereinafter, DL grant), HARQ information, a Downlink AssignmentIndex (DAI), a Transmit Power Control (TPC) command, etc. to each UE orUE group on a PDCCH. Information related to resource assignment carriedby a PDCCH may include RB assignment information, i.e. frequencyresource information, used for UL/DL transmission. The BS may allocatefrequency resources for a UE through the PDCCH.

The BS may transmit data to a UE or UE group in the data region. Datatransmitted in the data region is referred to as user data. A PDSCH maybe allocated to the data region for user data transmission. The PCH andthe DL-SCH are transmitted on the PDSCH. A UE may decode controlinformation received on a PDCCH and thus read data received on thePDSCH. The size and usage of control information transmitted on a PDCCHmay vary according to Downlink Control Information (DCI) formats and thesize of the control information may vary according to coding rates.Information indicating to which UE or UE group PDSCH data is transmittedand information indicating how the UE or UE group should receive anddecode the PDSCH data are transmitted on the PDCCH. For example, it isassumed that a specific PDCCH is CRC-masked with a Radio NetworkTemporary Identity (RNTI) ‘A’ and information about data transmittedusing a radio resource ‘B’ (e.g. frequency location) and using transportformat information ‘C’ (e.g. transmission block size, modulation scheme,coding information, etc.) is transmitted through a specific DL subframe.Then, the UE monitors the PDCCH using RNTI information thereof. The UEhaving the RNTI ‘A’ receives the PDCCH and receives the PDSCH indicatedby ‘B’ and ‘C’ through information of the received PDCCH.

A plurality of PDCCHs may be transmitted in the control region. A UE maymonitor the plurality of PDCCHs to detect a PDCCH thereof. Basically,the UE does not know the location at which a PDCCH thereof istransmitted. Therefore, the UE performs blind detection (referred alsoto as blind decoding) for all PDCCHs of a corresponding DCI format inevery subframe until a PDCCH having an identity thereof is received.

Meanwhile, as described with reference to FIG. 1, CA or bandwidthaggregation technology has recently been discussed. For example,referring to FIG. 1, five CCs, each of 20 MHz, may be aggregated on eachof UL and DL to support a bandwidth of 100 MHz. The respective CCs maybe contiguous or non-contiguous in the frequency domain. Forconvenience, FIG. 1 shows the case in which the bandwidth of a UL CC isthe same as the bandwidth of a DL CC and the two are symmetrical.However, the bandwidth of each CC may be independently determined It isalso possible to configure asymmetric CA in which the number of UL CCsis different from the number of DL CCs. A UL CC and a DL CC may also bereferred to as UL resources and DL resources, respectively. Even when aBS manages X DL CCs, a frequency bandwidth which can be received by aspecific UE may be limited to Y (≦X) DL CCs. In this case, the UE needsto monitor DL signals/data transmitted through the Y CCs. In addition,even when the BS manages L UL CCs, a frequency bandwidth which can bereceived by a specific UE may be limited to M (≦L) UL CCs. The limitedDL/UL CCs for a specific UE are referred to as serving UL/DL CCsconfigured in the specific UE. The BS may allocate a prescribed numberof CCs to the UE by activating some or all of the CCs managed by the BSor by deactivating some CCs managed by the BS. The BS may change theactivated/deactivated CCs and change the number of activated/deactivatedCCs. Various parameters for CA may be configured cell-specifically, UEgroup-specifically, or UE-specifically. Once the BS allocates availableCCs to the UE cell-specifically or UE-specifically, at least one of theallocated CCs is not deactivated, unless overall CC allocation to the UEis reconfigured or the UE is handed over. Hereinafter, the CC that isnot deactivated unless overall CC allocation to the UE is reconfiguredis referred to as a Primary CC (PCC) and a CC that the BS can freelyactivate/deactivate is referred to as a Secondary CC (SCC). Singlecarrier communication uses one PCC for communication between the UE andthe BS and does not use the SCC for communication. Meanwhile, the PCCand SCC may also be distinguished based on control information. Forexample, specific control information may be configured to betransmitted/received only through a specific CC. Such a specific CC maybe referred to as a PCC and the other CC (or CCs) may be referred to asan SCC (or SCCs). For instance, control information transmitted on aPUCCH may correspond to such specific control information. Thus, ifcontrol information transmitted on the PUCCH can be transmitted to theBS from the UE only through the PCC, a UL CC in which the PUCCH of theUE is present may be referred to as a UL PCC and the other UL CC (orCCs) may be referred to as a UL SCC (SCCs). As another example, if aUE-specific CC is used, the specific UE may receive a DL SynchronizationSignal (SS) from the BS as specific control information. In this case, aDL CC with which the specific UE establishes synchronization of initialDL time by receiving the DL SS (i.e. a DL CC used for attempting toaccess a network of the BS) may be referred to as a DL PCC and the otherDL CC (or CCs) may be referred to as a DL SCC (or SCCs). In a 3GPPLTE(-A) communication system, multicarrier communication uses one PCCand no SCC or one or more SCCs per UE. However, this is the definitionaccording to LTE(-A) and communication using multiple PCCs per UE willbe permitted in the future. The PCC may be referred to as a primary CC,an anchor CC, or a primary carrier and the SCC may be referred to as asecondary CC or a secondary carrier.

Meanwhile, 3GPP LTE(-A) uses the concept of cells to manage radioresources. A cell is defined as a combination of DL resources and ULresources, that is, a combination of a DL CC and a UL CC. The cell canbe configured of DL resources alone, or of both DL resources and ULresources. When CA is supported, a linkage between a carrier frequencyof the DL resources (or DL CC) and a carrier frequency of the ULresources (or UL CC) may be indicated by system information. Forexample, a combination of the DL resources and the UL resources may beindicated by a System Information Block type 2 (SIB2) linkage. In FDDusing different UL and DL operating bandwidths, different carrierfrequencies are linked to constitute one serving CC (or one servingcell) and the SIB2 linkage indicates a frequency of a UL CC using afrequency different from a frequency of a DL CC accessed by the UE. InTDD using the same UL and DL operating bandwidth, one carrier frequencyconstitutes one serving CC and the SIB linkage indicates a frequency ofa UL CC using the same frequency as a frequency of a DL CC accessed bythe UE.

Here, the carrier frequency refers to a center frequency of each cell orCC. A cell that operates on a primary frequency (or PCC) may be referredto as a Primary Cell (PCell) and a cell that operates on a secondaryfrequency (or SCC) may be referred to as a Secondary Cell (SCell). Theprimary frequency (or PCC) refers to a frequency (or CC) used for the UEto perform an initial connection establishment or connectionre-establishment procedure. PCell may refer to a cell indicated during ahandover process. The secondary frequency (or SCC) refers to a frequency(or CC) that is configurable after RRC connection setup is performed andis usable to provide additional radio resources. The PCell and SCell maybe collectively referred to as a serving cell. Accordingly, for a UE inan RRC_CONNECTED state, for which CA is not configured or CA is notsupported, only one serving cell comprised of only a PCell is present.Meanwhile, for a UE in an RRC_CONNECTED state, for which CA isconfigured, one or more serving cells may be present and the one or moreserving cells may include one PCell and one or more SCells. However, inthe future, it may be permitted that serving cells are configured toinclude a plurality of PCells. For CA, a network may configure one ormore SCells for a UE that supports CA in addition to the PCell initiallyconfigured in the connection establishment procedure after an initialsecurity activation procedure is initiated. However, even if the UEsupports CA, the network may configure only the PCell for the UE,without adding the SCells.

FIG. 5 illustrates exemplary DL scheduling when a plurality of carriersis aggregated.

In case of communication using a single carrier, only one serving cellis present and, therefore, a PDCCH carrying a UL/DL grant and aPUSCH/PDSCH corresponding to the PDCCH are transmitted in the same cell.In other words, in case of FDD in a single carrier, a PDCCH for a DLgrant for a PDSCH that is to be transmitted on a specific DL CC istransmitted on the specific DL CC and a PDCCH for a UL grant for a PUSCHthat is to be transmitted on a specific UL CC is transmitted on a DL CClinked to the specific UL CC.

On the contrary, in a multicarrier system, a plurality of cells may beconfigured and, therefore, transmission of a UL/DL grant in a servingcell having a good channel state may be permitted. Thus, if a cellcarrying the UL/DL grant, which scheduling information, is differentfrom a cell performing UL/DL transmission corresponding to the UL/DLgrant, this is referred to as cross-carrier scheduling. The 3GPP LTE(-A)system may support multicarrier aggregation and cross-carrier schedulingbased on multicarrier aggregation, for data transmission rateimprovement and stable control signaling.

Referring to FIG. 5, when cross-carrier scheduling (or cross-CCscheduling) is applied, a PDCCH for DL allocation for a DL CC B/C, i.e.a PDCCH carrying a DL grant, may be transmitted on a DL CC A and a PDSCHcorresponding to the PDCCH may be transmitted on a DL CC B/C. A CarrierIndicator Field (CIF) may be introduced for cross-CC scheduling. Whetherthe CIF is present in the PDCCH may be indicated semi-statically andUE-specifically (or UE group-specifically) through higher layersignaling (e.g. RRC signaling). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: PDCCH on a DL CC assigns PDSCH resources on the        same DL CC or PUSCH resources on a single linked UL CC.    -   No CIF    -   Same as LTE PDCCH structure (same coding and same Control        Channel Element (CCE)-based resource mapping) and DCI format    -   CIF enabled: PDCCH on a DL CC can assign PDSCH/PUSCH resources        on a specific DL/UL CC among multiple aggregated DL/UL CCs using        CIF.    -   Extended LTE DCI format with CIF    -   CIF (if configured) is a fixed x-bit field (e.g. x=3).    -   CIF (if configured) location is fixed regardless of DCI format        size.    -   Reuse of LTE PDCCH structure (same coding and same CCE-based        resource mapping)

One or more scheduling CCs may be configured for one UE and one of thescheduling CCs may be a PCC which is in charge of specific DL controlsignaling and UL PUCCH transmission. The scheduling CCs may beconfigured UE-specifically, UE-group-specifically, or cell-specifically.The scheduling CC may be configured so as to directly schedule at leastitself That is, the scheduling CC may become a scheduled CC thereof.Only one scheduling CC per scheduled CC may be configured. In otherwords, a plurality of scheduling CCs cannot be configured for onescheduled CC. In the present invention, a CC carrying a PDCCH isreferred to as a scheduling CC or a Monitoring CC (MCC) and a CCcarrying a PDSCH/PUSCH scheduled by the PDCCH is referred to as ascheduled CC.

The scheduling CC includes a DL CC among all aggregated DL CCs. The UEdetects/decodes the PDCCH only on a corresponding DL CC. That is, duringcross-CC scheduling, both DL and UL grant PDCCHs for scheduling PDSCHand PUSCH of the scheduling CC or scheduled CC may betransmitted/received only through the scheduling CC. A DL ACK/NACKchannel (or a PHICH in case of 3GPP LTE(-A)) carrying ACK/NACK for thePUSCH transmitted through the scheduling CC or scheduled CC may betransmitted/received only through the scheduling CC. ACK/NACK for thePDSCH transmitted through the scheduling CC or scheduled CC may betransmitted/received on a UL control channel (a PUCCH in case of 3GPPLTE(-A)) or a UL data channel (a PUSCH in case of 3GPP LTE(-A)). ThePUCCH may be transmitted on a PCC. In this case, the PDSCH/PUSCH of thescheduling CC or scheduled CC refers to a PDSCH/PUSCHconfigured/allocated to be transmitted on a corresponding CC. TheACK/NACK of the scheduling CC or scheduled CC refers to ACK/NACK fordata transmitted on a corresponding CC.

In TDD, most communication standards up to now consider onlymulticarrier aggregation having the same DL-UL configuration. If aplurality of aggregated CCs operates in the same DL-UL configuration,since DL/UL subframe (hereinafter SF) timings for all CCs are the same,a UL grant for scheduling a PUSCH of a scheduling/scheduled CC to betransmitted in a specific UL SF may be transmitted/received through a DLSF of the scheduling CC configured for transmission/reception of the ULgrant scheduling the PUSCH to be transmitted in the specific UL SF. Inaddition, for a PHICH transmission/reception timing for a PUSCHtransmitted through the scheduling CC and the scheduled CC in a specificUL SF, a PHICH transmission/reception timing configured in thecorresponding UL SF of the scheduling CC may be applied.

However, in consideration of the difference in UL/DL load on each CC andthe difference in channel state on each CC, it is preferable to permit adifferent DL-UL configuration per CC. If a plurality of CCs operating indifferent DL-UL configurations is aggregated and cross-CC scheduling issupported based on the aggregated CCs, a UL SF timing of the schedulingCC may differ from a UL SF timing of the scheduled CC. In other words,the scheduling CC and the scheduled CC in the same time resourceduration may operate not as DL and DL or UL and UL but as UL and DL orDL and UL. Then, a UL grant transmission/reception timing for PUSCHscheduling in each UL SF or an ACK/NACK transmission/reception timingfor PUSCH transmission in each UL SF may be independently configured perCC. Accordingly, if CA is configured based on different TDD DL-ULconfigurations, a UL grant transmission/reception timing configurationmethod and a DL ACK/NACK transmission/reception timing configurationmethod, for cross-scheduling, are needed.

Hereinafter, embodiments of the present invention will be describedunder the assumption of only aggregation of two CCs having differentDL-UL configurations, i.e. one scheduling CC and one scheduled CC.However, the embodiments of the present invention may be applied toaggregation of more than two CCs having different DL-UL configurations.In the following description, “D” indicates a DL SF or a special SF and“U” indicates a UL SF. “DD” represents an SF in which both a schedulingCC and a scheduled CC are configured with DL, “DU” represents an SF inwhich a scheduling CC is configured with DL and a scheduled CC isconfigured with UL, “UD” represents an SF in which a scheduling CC isconfigured with UL and a scheduled CC is configured with DL, and “UU”represents an SF in which both a scheduling CC and a scheduled CC areconfigured with UL.

<UL Grant Timing>

Hereinafter, UL grant transmission/reception timing for cross-schedulingof CCs having different DL-UL configurations according to embodiments ofthe present invention will be described. In the embodiments of thepresent invention, UL grant timing for a specific UL SF of a specific CCrefers to a DL SF of a CC configured such that a UL grant for schedulinga PUSCH transmitted in the specific UL SF of the specific CC istransmitted/received therein.

1. UL grant for PUSCH to be transmitted in UU and UD.

FIG. 6 illustrates an exemplary UL grant timing for PUSCH transmissionin a UU SF. Especially, FIG. 6 illustrates a radio frame in which DL-ULconfiguration #2 of Table 1 is applied to a scheduling CC and DL-ULconfiguration #6 of Table 1 is applied to a scheduled CC. In FIG. 6, anumber indicated in each DL SF represents a time point k_(PUSCH) atwhich a PUSCH corresponding to a DL grant received in a corresponding DLSF is to be transmitted. Table 3 shows k_(PUSCH) per TDD DL-ULconfiguration.

TABLE 3 TDD UL-DL DL subframe number n configuration 0 1 2 3 4 5 6 7 8 90 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 6 6 4 4 5 6 4 6 7 7 7 7

In Table 3, a number defined in a DL SF per DL-UL configurationcorresponds to k_(PUSCH). For example, referring to Table 3, k_(PUSCH)of a DL SF 3 in DL-UL configuration #2 is 4. Upon detecting a PDCCHcarrying a UL grant for the UE in an SF n, the UE may transmit a PUSCHin an SF _(n+k) _(PUSCH) according to k_(PUSCH) given in Table 3. InFIG. 6, a number indicated in each DL SF corresponds to k_(PUSCH) ofTable 3.

For reference, in FIG. 6, subframes of which subframe numbers have thesame value when a modulo-10 operation is applied thereto have the samelocation in each radio frame consisting of 10 subframes.

In a subframe configured with UU (hereinafter, UU SF) or a subframeconfigured with UD (hereinafter, UD SF), a scheduling CC basicallyincludes a UL SF (i.e. operates as UL) and, therefore, a UL grant timingfor a PUSCH to be transmitted in a UL SF of the scheduling CC exists inthe scheduling CC. Accordingly, with respect to a UL grant timing forscheduling a PUSCH of the scheduling CC and a PUSCH of a scheduled CC,transmitted in a specific UU SF or UD SF, a UL grant timing configuredfor the UL SF of the scheduling CC in the specific SF may be applied.That is, if the UL SF is configured on the scheduling CC in the specificSF, a UL grant for a PUSCH of the scheduled CC may be transmitted in aDL SF in which the UL grant for the PUSCH of the scheduling CC istransmitted.

Referring to FIG. 6, SFs #2, #7, #12, and #17 correspond to UU SFs. Forexample, UL grants for the scheduling CC and scheduled CC of SF #12 maybe transmitted through the scheduling CC in SF #8. In other words, a UEmay receive a UL grant(s) for the scheduling CC and/or scheduled CC fromthe BS in SF #8 on the scheduling CC and may transmit a PUSCH(s) throughthe scheduling CC and/or the scheduled CC in SF #12 which is ak_(PUSCH)-th (i.e. fourth) SF after SF #8.

2. UL grant for PUSCH to be transmitted in DU

In case of an SF configured with DU (hereinafter, DU SF), since thescheduling CC does not include a UL SF unlike the UU SF or UD SF, a ULgrant timing configured for the scheduling CC of the DU SF does notexist. Therefore, a UL grant timing for scheduling a PUSCH of thescheduled CC transmitted through the DU SF (i.e. SF #n) may beconfigured according to the following method.

-   -   Method 1: UL grant transmission/reception in a DL SF of a        scheduling CC which is a DL SF nearest to a corresponding SF        (i.e. SF #n) among SF # (n−m_(PUSCH)) and SFs prior to SF #        (n−m_(PUSCH))

Here, m_(PUSCH) represents a minimum SF interval (e.g. 4 SFs or 4 ms)between a UL grant timing and a PUSCH transmission timing. For example,if m_(PUSCH) is 4, the fourth SF after a DL SF in which a UL grant istransmitted or an SF corresponding to ‘DL SF, in which the UL grant istransmitted, +4 ms’ may be an SF in which the PUSCH can be transmitted.

-   -   Method 1 has an advantage of minimizing latency from UL grant        reception/transmission to PUSCH transmission/reception.

FIG. 7 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 1 of the present invention. Especially,FIG. 7 illustrates a UL grant timing for PUSCH transmission in a DU SF,when Method 1 is applied in the case where a scheduling CC and ascheduled CC operate in DL-UL configurations #2 and #6 of Table 1,respectively. It is assumed that m_(PUSCH) is four SFs. In FIG. 7, anumber indicated in each DL SF corresponds to k_(PUSCH) of Table 3.

Referring to FIG. 7, when a UL grant timing according to Method 1 of thepresent invention is applied to a PUSCH of a scheduled CC transmitted inSF #13, a UL grant for the PUSCH of the scheduled CC to be transmittedin SF #13 may be transmitted/received in a DL SF (i.e. SF #9) of thescheduling CC, which is a DL SF nearest to SF #13 among SF #(13−4) andSFs before SF #(13−4) on the scheduling CC. The BS may schedule thePUSCH to be transmitted through the scheduled CC in SF #13 to the UE bytransmitting the UL grant in SF #9. The UE may receive the UL grant inSF #9 and transmit the PUSCH corresponding to the UL grant in a UL SF ofthe scheduling CC, which is a UL SF nearest to SF #9 among SF #(9+4) andSFs after SF #(9+4).

-   -   Option 1: In application of Method 1, the DL SF of the        scheduling CC, which is nearest to SF #n among SF #(n−m_(PUSCH))        and SFs prior to SF #(n−m_(PUSCH)) may be determined from among        all DF SFs on the scheduling CC.    -   Option 2: Unlink Option 1, the DL SF of the scheduling CC, which        is nearest to SF #n among SF #(n−m_(PUSCH)) and SFs before SF        _(#)(n−m_(PUSCH)) on the scheduling CC may be determined among        only DL SFs in which UL grants are configured when the        scheduling CC operates as a single CC. For example, DL SFs in        which k_(PUSCH) is configured according to Table 3 are DL SFs in        which transmissions of UL grants in a single carrier system are        configured. A UE configured to communicate on a single carrier        attempts detection/decoding of a PDCCH not in all DL SFs but in        only DL SFs in which k_(PUSCH) is configured according to a        corresponding DL-UL configuration. In consideration of backward        compatibility with a single carrier system, a UL grant timing        for a PUSCH of a scheduled CC to be transmitted in a DU SF may        be restricted so that the UL grant timing may be determined        among DL SFs in which k_(PUSCH) is configured. In this case,        referring to FIG. 7, a DL SF which is nearest to SF #13 among SF        #(13−4) and SFs before SF #(13−4) on the scheduling CC is SF #8        and a UL grant for a PUSCH of the scheduled CC to be transmitted        in SF #13 is transmitted/received on the scheduling CC of SF #8.        On the contrary, for PDCCH load balancing, a DL SF for a UL        grant may be determined among DL SFs which are not configured to        transmit/receive the UL grant, i.e. DL SFs in which k_(PUSCH) is        not configured. In this case, referring to FIG. 7, SF #9 will be        a UL grant timing for the PUSCH of the scheduled CC to be        transmitted in SF #13.    -   Method 2: UL grant transmission/reception by applying a UL grant        timing for a UL SF of a scheduling CC, which is nearest to SF #n        among SFs before SF #n

FIG. 8 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 2 of the present invention. Particularly,FIG. 8 illustrates a UL grant timing for PUSCH transmission in a DU SF,when Method 2 is applied in the case where a scheduling CC and ascheduled CC operate in DL-UL configurations #2 and #6 of Table 1,respectively. In FIG. 8, a number indicated in each DL SF corresponds tokPUSCH of Table 3.

Referring to FIG. 8, when a UL grant timing according to Method 2 of thepresent invention is applied to a PUSCH of a scheduled CC transmitted inSF #13, a UL grant timing for a UL SF (i.e. SF #12) of the scheduling CCwhich is nearest to SF #13 among SFs prior to SF #13 may be used as a ULgrant timing for the scheduled CC of SF #13. Since the UL grant timingfor SF #12 of the scheduling CC is SF #8, the BS may transmit a UL grantfor the scheduled CC of SF #12 to the UE through the scheduling CC in SF#8. The UE may detect/receive a corresponding PDCCH by monitoring thescheduling CC in SF #8. Upon receiving the UL grant through thescheduling CC in SF #8, the UE transmits the PUSCH of the scheduled CCto the BS in SF #12 corresponding to SF #(8+k_(PUSCH)) (k_(PUSCH)configured in SF #8 is 4).

Method 2 of the present invention is advantageous in that a DL SF for ULgrant transmission/reception for the scheduling CC is one of DL SFsconfigured such that transmission/reception of a UL grant is alwaysallowed therein. That is, according to Method 2 of the presentinvention, the case does not occur in which DL SFs in whichtransmission/reception of the UL grant is not configured, for example,DL SFs without k_(PUSCH) in Table 3, are determined as DL SFs for ULgrant transmission/reception for the scheduled CC.

If Method 2 of the present invention is applied together with the ULgrant timing configuration method for the scheduled CC to be transmittedin a UU SF, a UL grant timing for the scheduled CC in a specific SF maybe determined based on a UL SF of the scheduling CC which is nearest tothe specific SF among the specific SF and SFs prior to the specific SF.For example, referring to FIG. 8, the UL grant timing for the scheduledCC of SF #12, which is a UU SF, may be determined based on a UL SF whichis nearest to SF #12 among SF #12 and SFs prior to SF #12 on thescheduling CC and the UL grant timing for the scheduled CC of SF #13which is a DU SF may be determined based on a UL SF which is nearest toSF #13 among the SF #13 and UL SFs prior to SF #13 on the scheduling CC.In other words, UL grant timing for the scheduling CC and scheduled CCmay be determined by applying the same rule to the UU SF, UD SF, and DUSF.

-   -   Method 3: UL grant transmission/reception in a DL SF of a        scheduling CC which is nearest to SF #n among a UL grant timing        corresponding to a UL SF of scheduled CC in SF #n and SFs prior        to the UL grant timing

FIG. 9 illustrates an exemplary UL grant timing for PUSCH transmissionin a DU SF according to Method 3 of the present invention. Especially,FIG. 9 illustrates a UL grant timing for PUSCH transmission in a DU SFwhen Method 3 is applied in the case in which a scheduling CC and ascheduled CC operate in DL-UL configurations #2 and #6 of Table 1,respectively. In FIG. 9, a number indicated in each DL SF corresponds tok_(PUSCH) of Table 3.

Referring to FIG. 9, if a UL grant timing according to Method 2 of thepresent invention is applied to a PUSCH of a scheduled CC transmitted inSF #13, a UL grant timing for a UL SF of the scheduled CC of SF #13,i.e. a UL SF (SF #6) of a scheduling CC which is nearest to SF #13 amongSF #6 and SFs prior to SF #6 may be used as the UL grant timing for thescheduled CC of SF #13. That is, the UL grant for the scheduling CC ofSF #13 may be transmitted/received through the scheduling CC in SF #6.

Option 1 or Option 2 described in Method 1 of the present invention mayalso be applied to Method 3 of the present invention in the same manner.

Up to now, methods for configuring the UL grant timing for the scheduledCC based on an SF have been described. Hereinafter, methods forconfiguring the UL grant timing for the scheduled CC based on a cell,i.e. a CC, will be described.

1. UL grant for PUSCH transmission of a scheduling CC

A UL grant timing for a UL SF in which a PUSCH is to be transmitted isapplied to a UL grant for the PUSCH to be transmitted through ascheduling CC.

2. UL grant for PUSCH transmission of a scheduled CC

A UL grant timing for a PUSCH of a scheduled CC to be transmitted in SF#n may be configured according to any one of the following methods.m_(PUSCH) and k_(PUSCH) used in the afore-mentioned Method 1, Method 2,and Method 3 have the same meaning as the following Method 1-1, Method2-1, and Method 3-1. Method 1-1, Method 2-1, and Method 3-1 respectivelycorrespond to Method 1, Method 2, and Method 3 for configuring the ULgrant timing for the scheduled CC based on an SF but the above-describedmethods and the following methods have different application criteria.Accordingly, the UL grant timing for the scheduled CC configuredaccording to Method 1/ Method 2/Method 3 may be different from the ULgrant timing for the scheduled CC configured according to Method 1-1/Method 2-1/Method 3-1.

-   -   Method 1-1: UL grant transmission/reception through a DL SF of a        scheduling CC which is nearest to SF #n among SF #(n−m_(PUSCH))        and SFs prior to SF #(n−m_(PUSCH))

Option 1 or Option2 described in Method 1 of the present invention mayalso be identically applied to Method 1-1 of the present invention.

-   -   Method 2-1: UL grant transmission/reception for a UL SF of a        scheduling CC which is nearest to SF #n among SF #n and SFs        prior to SF #n    -   Method 3-1: UL grant transmission/reception through a DL SF of a        scheduling CC which is nearest to SF #n among a UL grant timing        configured in a UL SF of the scheduled CC in SF #n and SFs prior        to the UL grant timing

Option 1 or Option 2 described in Method 1 of the present invention mayalso be identically applied to Method 3-1 of the present invention.

Meanwhile, if the afore-mentioned Method 1, Method 2, Method 3, Method1-1, Method 2-1, and Method 3-1 are applied, the case in which the sameUL grant timing for multiple UL SFs of the scheduled CC, i. e. amulti-grant timing, is configured may occur. That is, UL grants forscheduling PUSCHs of the scheduled CC to be transmitted in different ULSFs may be configured to be transmitted/received in the same DL SF ofthe scheduling CC. In this way, if a plurality of UL grants should betransmitted in one DL SF of one scheduling CC, the following methods maybe considered.

(1) Alt 1: A UL grant timing configured according to any one of theaforementioned Method 1, Method 2, Method 3, Method 1-1, Method 2-1, andMethod 3-1 is applied but, for a multi-grant timing, a field fordiscriminating/designating between SFs in a UL grant for PUSCHscheduling of the scheduled CC may be inserted. In this case, accordingto the number of UL grants capable of being transmitted/received at themulti-grant timing, the following schemes may be considered.

A. Alt 1-1: Single UL grant

In Alt 1-1 of the present invention, PUSCH scheduling information of ascheduled CC for one or more SFs is transmitted/received using one ULgrant, i.e. one PDCCH. According to Alt 1-1 of the present invention,only one UL grant may be transmitted/received for the scheduled CC in aDL SF of the scheduling CC, corresponding to a multi-grant timing. Afield (of a bitmap type for example) for discriminating between SFs inwhich the scheduled CC is scheduled may be inserted in a correspondingUL grant. In this case, in order to prevent PHICH transmissions formultiple PUSCHs for the scheduled CC from colliding, the BS may allocateadditional information (e.g. PHICH offset) for discriminating betweendifferent DeModulation Reference Signals (DMRSs) or PHICH resources perPUSCH of the scheduled CC. For example, in allocating PHICH resources, aDMRS may be explicitly allocated only to a specific PUSCH of thescheduled CC and may be implicitly allocated (i.e. according topredesignated offset) to the other PUSCHs of the scheduled CC.

B. Alt 1-2: multiple UL grants

In Alt 1-2 of the present invention, one UL grant, i.e. only PUSCHscheduling information of the scheduled CC for one SF, is transmitted onone PDCCH. According to Alt 1-2 of the present invention, a plurality ofgrants may be transmitted/received in a DL SF of the scheduling CC,which is corresponding to a multi-grant timing. A field (a form slimierto a CIF indicating a CC during cross-CC scheduling for example)indicating an SF in which a PUSCH of the scheduled CC is to betransmitted may be inserted to a corresponding UL grant.

Alt 2: Modifications of Method 1, Method 2, and Method 3 or Method 1-1,Method 2-1, and Method 3-1 may be applied in units of an SF Group (SFG)comprised of consecutive UL SFs of the scheduled CC (hereinafter, ascheduled CC-U SFG). It is assumed that the number of SFs included inthe scheduled CC-U SFG is N (where N is a positive integer) and a firstSF number included in the scheduled CC-U SFG is SF #n.

-   -   Method 1-2: M (≦N) (where M is a positive integer) DL SF(s) of        the scheduling CC, which are nearest to a corresponding SF, i.e.        SF #n, among SF #(n−m_(PUSCH)) and SFs prior to SF        #(n−m_(PUSCH)) may be configured as UL grant timings for N UL        SF(s) of the scheduled CC in a scheduled CC-U SFG. UL grant        timings for all or some UL SF(s) of the scheduled CC may be        repeatedly configured in one DL SF of the scheduling CC. When        M=N, N DL SF(s) of the scheduling CC may be linked to N UL SF(s)        of the scheduled CC one by one.

Option 1 or Option 2 described in Method 1 of the present invention maybe identically applied to the present Method 1-2.

-   -   Method 2-2: UL grant timings for M (≦N) UL SF(s) of the        scheduling CC, which are nearest to a corresponding SF, i.e. SF        #n, among SF #n and SFs prior to SF #n may be configured as UL        grant timing(s) of N UL SF(s) of the scheduled CC in a scheduled        CC-U SFG. UL grant timings for all or some UL SF(s) of the        scheduled CC may be repeatedly configured in one DL SF. When        M=N, N DL SF(s) of the scheduling CC may be linked to N UL SF(s)        of the scheduled CC in time order one by one.    -   Method 3-2: M (≦N) DL SF(s) of the scheduling CC, which are        nearest to SF #n among a UL grant timing of the scheduled CC,        configured in a UL SF of the scheduled CC in SF #n, and SFs        prior to the UL grant timing may be configured as UL grant        timings of N UL SF(s) of the scheduled CC in a scheduled CC-U        SFG. UL grant timing(s) for all or some UL SF(s) of the        scheduled CC may be repeatedly configured in one DL SF of the        scheduling CC. When M=N, N DL SF(s) of the scheduling CC may be        linked to N UL SF(s) of the scheduled CC in time order one by        one.

Option 1 or Option 2 described in Method 1 of the present invention mayalso be identically applied to Method 3-2 of the present invention.

In a DL SF of a scheduling CC, corresponding to a UL grant timingdetermined according to one of the above methods of the presentinvention, the UE blind-decodes a PDCCH search space in order to detecta PDCCH for the UE. The UE is configured to blind-decode both a searchspace for the scheduling CC and a search space of the scheduled CC in aDL SF of the scheduling CC corresponding to a UL grant timing for a UUSF. The UE is configured to blind-decode a search space for thescheduling CC in a DL SF of the scheduling CC corresponding to a ULgrant timing for a UD SF and to blind-decode a search space for thescheduled CC in a DL SF of the scheduling CC corresponding to a UL granttiming for a DU SF.

<PHICH Timing>

Hereinafter, embodiments of the present invention of a DL ACK/NACKtransmission/reception timing in a cross-CC scheduling situation of CCshaving different DL-UL configurations will be described. In theembodiments of the present invention of the DL ACK/NACKtransmission/reception timing, a PHICH timing for a specific UL SF of aspecific CC refers to a DL SF of a CC configured to transmit/receive aPHICH for a PUSCH transmitted in a corresponding UL SF of the CC.

3. PHICH for PUSCH to be transmitted in UU and UD

FIG. 10 illustrates an exemplary PHICH timing for PUSCH transmission ina UU SF. Particularly, FIG. 10 illustrates a radio frame in which DL-ULconfiguration #1 of Table 1 is applied to a scheduling CC and DL-ULconfiguration #6 of Table 1 is applied to a scheduled CC. In FIG. 10, anumber indicated in each UL SF represents a time point k_(PHICH) atwhich a PHICH corresponding to a PUSCH in a corresponding UL SF is to betransmitted. Table 4 shows k_(PHICH) in each TDD DL-UL configuration.

TABLE 4 TDD UL-DL UL subframe number n configuration 0 1 2 3 4 5 6 7 8 90 4 7 6 4 7 6 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 4 6 6 4 7

In Table 4, numbers defined in UL subframes in each DL-UL configurationcorrespond to k_(PHICH). For example, referring to Table 4, k_(PHICH) ofa UL SF 2 in DL-UL configuration #2 is 6. For PUSCH transmissionscheduled in an SF n, a UE determines a PHICH resource in an SF _(n+k)_(PHICH). That is, in FIG. 10, a number denoted in each UL SFcorresponds to k_(PHICH) of Table 4.

In Table 4, k_(PHICH) defines a corresponding PHICH timing based on a ULSF in which a PUSCH is transmitted. k_(PHICH) may be redefined as a newparameter (hereinafter, k) defining a corresponding PUSCH transmissiontiming based on a DL SF in which a PHICH is transmitted. Table 5 shows kin each TDD DL-UL configuration.

TABLE 5 TDD DL-UL DL subframe number i configuration 0 1 2 3 4 5 6 7 8 90 7 7 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

In Table 5, a number defined in a DL SF per DL-UL configurationcorresponds to k. For example, referring to Table 5, k of a DL SF 3 inDL-UL configuration #2 is 6. ACK/NACK received on a PHICH allocated to aUE in an SF i is associated with PUSCH transmission in an SF i-kaccording to k_(PHICH) indicated by Table 4. For instance, the UE maytransmit a PUSCH to the BS in a subframe i-k and receive a PHICH for thePUSCH from the BS in the subframe i. That is, in FIG. 10, a numberdenoted in each DL SF corresponds to k of Table 5.

Referring to Tables 4 and 5, the DL SF i of Table 5 corresponds to a DLSF n+k_(PHICH) of Table 4 and a DL subframe i-k of Table 5 correspondsto a UL SF n of Table 4. That is, a number denoted in each DL SFcorresponds to k of Table 5.

For reference, in FIG. 10, subframes of which subframe numbers has thesame results when a modulo-10 operation is applied thereto have the samelocation in each radio frame comprised of 10 subframes.

Since a scheduling CC in a UU SF or UD SF basically includes a UL SF, aPHICH timing for the above SF is configured. Accordingly, a PHICH timingconfigured for a UL SF of the scheduling CC in a specific SF may becommonly applied to PHICH timings for a PUSCH of a scheduling CC and aPUSCH of a scheduled CC, transmitted in a specific SF configured withthe UU or UD SF. That is, if the UL SF is configured on the schedulingCC in a specific SF, a PHICH for the PUSCH of the scheduled CC may betransmitted in a DL SF in which a PHICH for the PUSCH of the schedulingCC is transmitted.

Referring to FIG. 10, SF #2, SF #3, SF #7, SF #8, SF #12, SF #13, SF#17, and SF #18 correspond to UU SFs. For example, PHICHs for a PUSCH ofthe scheduling CC transmitted in SF #8 and/or a PUSCH of the scheduledCC transmitted in SF #8 may be transmitted through the scheduling CC inSF #14. In other words, the UE which has transmitted the PUSCH of thescheduling CC and the PUSCH of the scheduled CC in SF #8 may receive aPHICH for the PUSCH of the scheduling CC and a PHICH for the PUSCH ofthe scheduled CC in SF #14, which is the sixth SF (k_(PHICH)=6) after SF#8, from the BS. The UE and the BS may reconfigure k_(PHICH) for a UL SFof the scheduled CC according to this embodiment. For example, referringto FIG. 10, the UE and the BS may reconfigure k_(PHICH) for SF #8 of thescheduled CC as 6.

4. PHICH for PUSCH to be transmitted in DU.

In a DU SF, since the scheduling CC does not include a UL SF unlike a UUSF or UD SF, a PHICH timing configured for the scheduling CC of the DUSF does not exist. Accordingly, a PHICH timing corresponding to thePUSCH of the scheduling CC transmitted through the DU SF (i.e. SF #n)may be configured according to the following method.

-   -   Method 4: PHICH transmission/reception in a first DL SF of a        scheduling CC among SF #(n+m_(PHICH)) or SFs after SF        #(n+m_(PHICH))

Here, m_(PHICH) means a minimum SF interval (e.g. 4 SFs or 4 ms) betweena PUSCH transmission timing and a PHICH timing. For example, if mPHICHis 4, the fourth SF after a UL SF in which a PUSCH is transmitted or anSF corresponding to ‘UL SF, in which the PUSCH is transmitted, +4 ms’corresponds to an SF in which the PHICH can be transmitted.

Method 4 of the present invention has an advantage of minimizing latencyfrom PUSCH transmission/reception to PHICH reception/transmission.

FIG. 11 illustrates an exemplary PHICH timing for PUSCH transmission ina DU SF according to Method 4 of the present invention. Particularly,FIG. 11 illustrates an example of a PHICH grant timing for PUSCHtransmission in a UL SF when Method 4 is applied in the case in which ascheduling CC and a scheduled CC operate in DL-UL configurations #1 and#6 of Table 1, respectively. In this case, m_(PHICH) is assumed to befour SFs. In FIG. 11, a number denoted in each UL SF corresponds tok_(PHICH) of Table 4 and a number denoted in each DL SF corresponds to kof Table 5.

Referring to FIG. 11, if a PHICH timing according to Method 4 of thepresent invention is applied to a PUSCH of a scheduled CC transmitted inSF #4, a PHICH for the PUSCH transmitted in SF #4 may betransmitted/received in the first DL SF of the scheduling CC among SF#(4+4) and SFs after SF #(4+4), i.e. in SF #9. The BS may transmit thePHICH for the PUSCH received through the scheduled CC in SF #4 to the UEin SF #9. The UE may transmit the PUSCH on the scheduled CC in SF #4 anddetect/receive the PHICH for the PUSCH in the first DL SF of thescheduled CC among SF #(4+4) and SFs after SF #(4+4), i.e., in SF #6.The UE and the BS may reconfigure k_(PHICH) for a UL SF of the scheduledCC according to the present invention. For example, referring to FIG.11, the UE and the BS may reconfigure k_(PHICH) for SF #4 of thescheduled CC as 5.

-   -   Option 3: The first DL SF of the scheduling CC among SF        #(n+m_(PHICH)) and SFs after SF #(n+m_(PHICH)) may be determined        from among DL SFs configured such that a PHICH may be        transmitted/received therein when only the scheduling CC        operates as a single CC. That is, a PHICH timing of the present        invention may be determined from among DL SF(s) in which PHICH        resource(s) is/are reserved from among DL SFs of the scheduling        CC because the PHICH regions/resource(s) may be        cell-specifically configured/allocated. For example, in Table 5,        DL SFs in which k is configured are DL SFs in which the PHICH        resource is reserved. The UE attempts to detect/receive a PHICH        not in all DL SFs but in DL SFs in which k is configured        according to a corresponding DL-UL configuration. In this case,        referring to FIG. 11, the first DL SF in which k is configured        among SF #(4+4) and DL SFs of the scheduling CC after SF #(4+4)        is SF #9 and a PHICH for a PUSCH of the scheduled CC transmitted        in SF #4 is transmitted/received on the scheduling CC of SF #9.    -   Option 4: A first DL SF of a scheduling CC among SF        #(n+m_(PHICH)) or SFs SF #(n+m_(PHICH)) may be determined among        all DL SFs of the scheduling CC. Notably, although the PHICH        timing is determined from among all DL SFs of the scheduling CC,        the PHICH may not be transmitted/received in DL SFs in which the        PHICH resource is not reserved, for example, in DL SFs without k        in Table 5. According to the present invention, if the PHICH        resource cannot be allocated to a DL SF configured as the PHICH        timing, the BS does not transmit the PHICH in the DL SF.        According to the present invention, if the PHICH resource is not        present in a DL SF configured as the PHICH timing, the UE does        not attempt to detect/receive the PHICH in the DL SF. In 3GPP        LTE(-A), ACK/NACK for a PUSCH is signaled to the UE by two        schemes. One scheme uses an ACK/NACK signal transmitted through        a PHICH and the other scheme uses a New Data Indicator (NDI)        transmitted through a PDCCH. Upon receiving NACK through the        PHICH, the UE may recognize that the PUSCH has not been        successfully received by the BS and retransmission of the PUSCH        is needed. If an NDI in the PDCCH is toggled compared to a        previous NDI, the UE recognizes that previous PUSCH transmission        is successful and empties a buffer which has stored data packets        corresponding to the PUSCH. On the other hand, the NDI in the        PDCCH is not toggled compared to the previous NDI, the UE        recognizes that previous PUSCH transmission fails and existing        data needs to be retransmitted. Therefore, according to Option 4        of the present invention, if a UL grant demanding        retransmission, i.e. a grant having an NDI not toggled, is not        received, the UE does not perform retransmission of the        previously transmitted PUSCH. In other words, the UE may perform        retransmission for the previously transmitted PUSCH according to        content included in the UL grant only when a UL grant demanding        retransmission (UL grant including an NDI not toggled) is        received.    -   Option 5: Similarly to Option 4, in Option 5, a PHICH timing is        determined from among all DL SFs of the scheduling CC and a        PHICH is not transmitted/received in DL SFs in which a PHICH        resource is not reserved. However, in Option 5, adaptive        retransmission according to an NDI configured in a UL grant is        not performed. Instead, non-adaptive retransmission performed        without the UL grant is performed. The following scheme may be        considered so that a PUSCH of the scheduled CC may be        retransmitted without the UL grant.

Alt 1: Method using UL grant

If a UL grant is not received, the UE recognizes that a PUSCH of thescheduled CC is NACK and may retransmit the PUSCH. If a value explicitlyindicating ACK (and/or NACK) information for a corresponding PUSCH isadditionally inserted into the UL grant or if a specific field (or acombination of specific fields) in the UL grant is invalid or isconfigured as a predetermined value (or a combination of predeterminedvalues) (and/or an NDI is not toggled), the UE may be configured toassume it as ACK for the PUSCH. Upon recognizing ACK, the UE may stopretransmission of the PUSCH. For example, upon receiving invalidresource allocation information and an NDI not toggled, the UE mayrecognize that the BS has successfully received the PUSCH of thescheduled CC and determines that the PUSCH does not need to betransmitted. Unlike Option 4, the UE assumes that PUSCH transmission ofthe scheduled CC is NACK until the UL grant is received.

Alt 2: Method using a specific CCE resource in PDCCH region

An entire region in which a PDCCH is transmitted in each DL SF iscomprised of a plurality of CCEs and a PDCCH transmitted to the UE isconfigured to include one or more CCEs. A specific CCE resource in apredesignated PDCCH region may be used for PHICH transmission/receptionfor the PUSCH of the scheduled CC. The CCE resource used for PHICHtransmission/reception may be UE-specifically allocated through RRC orL1 or L2 signaling.

-   -   Method 5: PHICH transmission/reception applying a PHICH timing        for the first UL SF of a scheduling CC after SF #n

FIG. 12 illustrates an exemplary PHICH timing for PUSCH transmission ina DU SF according to Method 5 of the present invention. Especially, FIG.12 illustrates a PHICH timing for PUSCH transmission in a DU SF whenMethod 5 is applied in the case in which a scheduling CC and a scheduledCC operate in DL-UL configurations #1 and #6 of Table 1, respectively.In FIG. 12, a number indicated in each UL SF corresponds to k_(PHICH) ofTable 4 and a number indicated in a DL SF corresponds to k of Table 5.

Referring to FIG. 12, when a PHICH timing according to Method 4 of thepresent invention is applied to a PUSCH of the scheduled CC transmittedin SF #4, a PHICH timing for the first UL SF (i.e. SF #7) of thescheduling CC among SF #4 and SFs after SF #4 may be used as a PHICHtiming for the scheduled CC of SF #4. The BS which has received a PUSCHthrough the scheduled CC in SF #4 transmits a PHICH for the PUSCH of thescheduled CC to the UE through the scheduling CC in SF #11 correspondingto SF #(7+k_(PHICH)) (k_(PHICH) configured in SF #4 is 4). Since thePHICH timing for SF #7 of the scheduling CC is SF #(7+4) (=SF #11), theUE may detect/receive the PHICH for the PUSCH of the scheduled CCtransmitted to the BS through the scheduling CC in SF #11.

Method 5 of the present invention is advantageous in that a DL SF fortransmitting/receiving the PHICH for the scheduled CC is one of DL SFsconfigured to always transmit/receive the PHICH. That is, according toMethod 4 of the present invention, the case does not occur in which a DLSF which is not configured to transmit/receive the PHICH is notconfigured, for example, a DL SF without k in Table 4, is determined asa DL SF for PHICH transmission/reception on the scheduled CC.

If Method 5 of the present invention is applied together with the PHICHtiming configuration method for the scheduled CC to be transmitted in aUU SF, a PHICH timing for the scheduled CC in a specific SF may bedetermined based on the first UL SF of the scheduling CC among thespecific SF and SFs after the specific SF. For example, referring toFIG. 12, a PHICH timing for the scheduled CC of SF #7 which is a UU SFmay be determined based on the first UL SF among UL SFs of thescheduling CC including SF #7 and a PHICH timing for the scheduled CC ofSF #4 which is a DU SF may also be determined based on the first UL SFamong UL SFs of the scheduling CC including SF #7. In other words, PHICHtimings for the scheduling CC and the scheduled CC may be determined byapplying the same rule to the UU SF, UD SF, and DU SF.

-   -   Method 6: PHICH transmission/reception in the first DL SF of a        scheduling CC among a PHICH timing for a UL SF of a scheduled CC        in SF #n and SFs after the PHICH timing

FIG. 13 illustrates an exemplary PHICH timing for PUSCH transmission ina DU SF according to Method 6 of the present invention. Especially, FIG.13 illustrates a PHICH timing for PUSCH transmission in a DU SF whenMethod 6 is applied in the case in which a scheduling CC and a scheduledCC operate in DL-UL configurations #1 and #6 of Table 1, respectively.In FIG. 12, a number indicated in each UL SF corresponds to k_(PHICH) ofTable 4 and a number indicated in a DL SF corresponds to k of Table 5.

Referring to FIG. 13, if a PHICH timing according to Method 6 of thepresent invention is applied to a PUSCH of the scheduled CC transmittedin SF #4, a PHICH timing for a UL SF of the scheduled CC of SF #4, i.e.the first DL SF of the scheduling CC among SF #(4+6) (=SF #10) and SFsafter SF #(4+6) may be used as a PHICH timing for the scheduled CC of SF#4. Namely, the PHICH for the scheduled CC of SF #4 may betransmitted/received through the scheduling CC in SF #10. Therefore,k_(PHICH) for the UL SF of the scheduling CC in SF #4 may bereconfigured as 6.

Option 3, Option 4, or Option 5 described in Method 4 of the presentinvention may also be identically applied to Method 6 of the presentinvention.

Up to now, methods for configuring the PHICH timing for the scheduled CCbased on an SF have been described. As another method, PHICH timingconfiguration methods for the scheduled CC based on a cell, i.e. a CC,will be described.

4. PHICH for PUSCH transmission of scheduling CC

For a PHICH for a PUSCH to be transmitted through the scheduling CC, aPHICH timing for a UL SF in which the PUSCH is transmitted is applied.

5. PHICH for PUSCH transmission of a scheduled CC

A UL grant timing for the PUSCH of the scheduled CC to be transmitted inSF #n may be configured according to any one of the following methods.m_(PHICH) and k_(PHICH) used in the above-described Method 4, Method 5,and Method 6 may have the same meaning in the following Method 4-1,Method 5-1, and Method 6-1. Method 4-1, Method 5-1, and Method 6-1correspond to Method 4, Method 5, and Method 6, respectively, forconfiguring a UL grant timing for the scheduled CC based on an SF butdiffer in application criteria. Therefore, the UL grant timing for thescheduled CC configured according to Method 4/Method 5/Method 6 may bedifferent from the UL grant timing for the scheduled CC configuredaccording to Method 4-1/Method 5-1/Method 6-1.

-   -   Method 4-1: PHICH transmission/reception through a first DL SF        of scheduling CC among SR #(n+m_(PHICH)) and SFs after SF        #(n+m_(PHICH))

Option 3, Option 4, or Option 5 described in Method 4 of the presentinvention may also be identically applied to Method 4-1 of the presentinvention.

-   -   Method 5-1: PHICH transmission/reception by applying a PHICH        timing for the first UL SF of a scheduling CC among SF #n and        SFs after SF #n    -   Method 6-1: PHICH transmission/reception through the first DL SF        of a scheduling CC among a PHICH timing of a scheduled CC        configured in a UL SF of the scheduled CC in SF #n and SFs after        the PHICH timing

Option 3, Option 4, or Option 5 described in Method 4 of the presentinvention may also be identically applied to Method 4-1 of the presentinvention.

According to the above-described Method 4, Method 5, Method 6, Method4-1, Method 5-1, and Method 6-1, the case in which the same PHICHtiming, i.e. a multi-PHICH timing, is configured for UL SFs of aplurality of scheduled CCs may occur. That is, PHICHs for PUSCHs of thescheduled CC transmitted in different UL SFs may be configured totransmit/receive the same DL SF of the scheduling CC. Thus, when aplurality of PHICHs should be transmitted in one DL SF of one schedulingCC, modified forms of Method 4, Method 5, and Method 6 or Method 4-1,Method 5-1, and Method 6-1 may be applied in the unit of an SF group(i.e. scheduled CC-U SFG) consisting of consecutive UL SFs of thescheduled CC. It is assumed that the number of SFs included in thescheduled CC-U SFG is N (where N is a positive integer) and the last SFnumber included in the scheduled CC-U SFG is #n.

-   -   Method 4-2: First M(≦N) (where M is a positive integer) DL SF(s)        of the scheduling CC among SF #(n+m_(PHICH)) and SFs after SF        #(n+m_(PHICH)) may be configured as PHICH timing(s) for UL SF(s)        in the scheduled CC-U SFG. PHICH timings for all or some UL        SF(s) of the scheduled CC may be repeatedly configured in one DL        SF of the scheduling CC. If M=N, N DL SF(s) of the scheduling CC        may be linked to N UL SF(s) of the scheduled CC one by one in        time order.

Option 3, Option 4, or Option 5 described in Method 4 of the presentinvention may also be identically applied to Method 4-2 of the presentinvention.

-   -   Method 5-2: First M (≦N) (where M is a positive integer) UL SFs        of the scheduling CC among SF #n and SFs after SF #n may be        configured as PHICH timing(s) for N UL SF(s) in the scheduled        CC-U SFG. PHICH timings for all or some UL SFs of the scheduled        CC may be configured in one DL SF. If M=N, N DL SF(s) of the        scheduling CC may be linked to N UL SF(s) of the scheduled CC        one by one in time order.    -   Method 6-2: First M(≦N) (where M is a positive integer) DL SFs        of the scheduling CC among a PHICH timing of the scheduled CC        configured in a UL SF of the scheduled CC in SF #n and DL SFs        after the PHICH timing may be configured as UL grant timings for        N UL SF(s) in the scheduled CC-U SFG. PHICH timing(s) for all or        some UL SF(s) of the scheduled CC may be repeatedly configured        in one DL SF of the scheduled CC. If M=N, N DL SF(s) of the        scheduling CC may be linked to N UL SF(s) of the scheduled CC        one by one in time order.

Option 3, Option 4, or Option 5 described in Method 4 of the presentinvention may also be identically applied to Method 6-2 of the presentinvention.

Meanwhile, a DL SF configured for transmission/reception of a PHICH forthe scheduling CC operating as a single CC, for example, referring toTable 5, a DL SF in which k is configured, is assumed to be aPHICH-configured SF and a DL SF which does not correspond to thePHICH-configured SF is assumed to be a non-PHICH-configured SF.According to the above-described Method 4, Method 5, Method 6, Method4-1, Method 5-1, Method 6-1, Method 4-2, Method 5-2, and Method 6-2, thenon-PHICH-configured SF may be configured as a PHICH timing for a UL SFof a specific scheduled CC. If the non-PHICH-configured SF is configuredas a PHICH timing, the method of omitting PHICH transmission/receptionand retransmitting the PUSCH as in Option 4 or the method of omittingPHICH transmission/reception and non-adaptively retransmitting the PUSCHas in Option 5 may be applied.

<UL grant timing> and <PHICH timing> according to the proposed methodsof the present invention may be simultaneously applied.

FIG. 14 illustrates a UL grant timing and a PHICH timing for PUSCHtransmission in a DL SF according to the present invention. Especially,FIG. 14 illustrates a UL grant timing and a PHICH timing for PUSCHtransmission in a DU SF when Method 2 and Method 5 are applied in thecase in which a scheduling CC and a scheduled CC operate in DL-ULconfigurations #2 and #6 of Table 1, respectively. In FIG. 14, a numberindicated in each DL SF of the scheduling CC corresponds to kPHICH ofTable 3 and a number indicated in a UL SF corresponds to k_(PHICH) ofTable 4.

Referring to FIG. 14, a UL grant for a PUSCH to be transmitted throughthe scheduled CC in SF #8 may be transmitted/received in a UL granttiming, SF #3, for a UL SF (SF #7) of the scheduling CC, which isnearest to SF #8 among SF #8 and SFs after SF #8, according to Method 2of the present invention. A PHICH for the PUSCH transmitted to the BSthrough the scheduled CC in SF #8 may be transmitted/received in a PHICHtiming (SF #(12+6)=SF #18) for SF #12 which is the first UL SF of thescheduling CC among SF #8 and SFs after SF#8 according to Method 5 ofthe present invention.

Meanwhile, according to any one of the methods of the preset inventionrelated to <UL grant timing>, a DL SF of the scheduling CC correspondingto a UL grant timing for the scheduled CC may be used totransmit/receive a PHICH for a PUSCH of the scheduled CC. Similarly,according to any one of the methods of the present invention related to<PHICH timing>, a DL SF of the scheduling CC corresponding to a PHICHtiming for the scheduled CC may be used to transmit/receive a UL grantfor the scheduled CC. For example, referring to FIG. 14, a PHICH for aPUSCH in SF #8 and a UL grant for retransmission of the PUSCH or a ULgrant for transmission of a new PUSCH may be transmitted/received in aPHICH timing SF #18 configured according to Method 5 of the presentinvention. In addition, for a PUSCH to be transmitted in SF #8, a ULgrant timing SF #3 configured according to Method 2 of the presentinvention may be used as a PHICH timing for a PUSCH transmitted to theBS in a previous frame.

On the other hand, the proposed methods of the present invention relatesto <UL grant timing> and <PHICH timing> may be applied to each of aplurality of scheduled CCs having different DL-UL configurations. Inother words, if plural scheduled CCs have different DL-UL configurationsfrom a PCC, the above described methods of the present invention may beapplied to respective scheduling and scheduled CCs. That is, if ascheduled CC has a different DL-UL configuration from a scheduling CC interms of one scheduled CC, the proposed methods of the present inventionmay be applied.

FIG. 15 is a block diagram illustrating elements of a BS 10 and a UE 20by which the present invention is performed.

In the above-described methods of the present invention, the BS 10 maybe a transmission entity of a PHICH and/or a UL grant and the UE 20 maybe a transmission entity of a PUSCH. Therefore, the BS 10 may transmit aUL grant for a scheduling CC and/or a scheduled CC to the UE on thescheduling CC at a UL grant timing determined according to any one ofthe above methods of the present invention. To receive a PDCCH for theUE 20 at the UL grant timing determined according to any one of theabove methods, the UE 20 blind-detects/decodes a corresponding searchspace of a PDCCH region of the scheduled CC. The UE 20 may receive thePDCCH and transmit a corresponding PUSCH to the BS 10 through thescheduling CC or the scheduled CC according to the UL grant carried onthe PDCCH. The BS 10 may transmit a PHICH for the PUSCH received fromthe UE 20 through the scheduling CC and/or the scheduled CC to the UE 20at a PHICH timing determined according to any one the above methods ofthe present invention. The UE 20 may detect/receive, on the schedulingCC at a PHICH timing determined according to any one the above methodsof the present invention, the PHICH for the PUSCH transmitted to the BS10 through the scheduling CC and/or the scheduled CC.

The BS 10 and the UE 20 respectively include Radio Frequency (RF) units13 and 23 capable of transmitting and receiving radio signals carryinginformation, data, signals, and/or messages, memories 12 and 22 forstoring information related to communication in a wireless communicationsystem, and processors 11 and 21 operationally connected to elementssuch as the RF units 13 and 23 and the memories 12 and 22 to control theelements and configured to control the memories 12 and 22 and/or the RFunits 13 and 23 so as to perform at least one of the above-describedembodiments of the present invention.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily storing input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 control the overall operation of variousmodules in the BS or UE. The processors 11 and 21 may perform variouscontrol functions to perform the present invention. The processors 11and 21 may be referred to as controllers, microcontrollers,microprocessors, or microcomputers. The processors 11 and 21 may beimplemented by hardware, firmware, software, or a combination thereof.In a hardware configuration, Application Specific Integrated Circuits(ASICs), Digital Signal Processors (DSPs), Digital Signal ProcessingDevices (DSPDs), Programmable Logic Devices (PLDs), or FieldProgrammable Gate Arrays (FPGAs) may be included in the processors 11and 21. If the present invention is implemented using firmware orsoftware, the firmware or software may be configured to include modules,procedures, functions, etc. performing the functions or operations ofthe present invention. Firmware or software configured to perform thepresent invention may be included in the processors 11 and 21 or storedin the memories 12 and 22 so as to be driven by the processors 11 and21.

The processor 11 of the BS codes and modulates signals and/or datascheduled by the processor 11 or a scheduler connected to the processor11 to be transmitted to the exterior. The coded and modulated signalsand/or data are transmitted to the RF unit 13. For example, theprocessor 11 converts a data stream to be transmitted into K layersthrough demultiplexing, channel coding, scrambling and modulation. Thecoded data stream is also referred to as a codeword and is equivalent toa transport block which is a data block provided by a Medium AccessControl (MAC) layer. One Transport Block (TB) is coded into one codewordand each codeword is transmitted to the receiving device in the form ofone or more layers. For frequency up-conversion, the RF unit 13 mayinclude an oscillator. The RF unit 13 may include N_(t) (where N_(t) isa positive integer) transmit antennas. The processor 11 may determine aUL grant timing according to one method of the present invention. The RFunit 13 may transmit a UL grant for a scheduling CC or a scheduled CC tothe UE 20 on the scheduling CC at the UL grant timing configuredaccording to one method of the present invention, under the control ofthe processor 11. The RF unit 13 may receive a PUSCH scheduled on thescheduling CC or scheduled CC by the UL grant from the UE 20 through acorresponding CC in a UL SF associated with the UL grant timing. Theprocessor 11 may configure/determine an SF, i.e. a PHICH timing, totransmit a PHICH carrying ACK/NACK for the PUSCH. The RF unit 13 maytransmit the PHICH for the PUSCH to the UE through the scheduling CC inthe PHICH timing configured/determined according to one method of thepresent invention, under the control of the processor 11.

A signal processing process of the UE 20 is the reverse of the signalprocessing process of the BS 10. Under control of the processor 21, theRF unit 23 of the UE 10 receives radio signals transmitted by the BS 10.The RF unit 23 may include N_(r) receive antennas and frequencydown-converts each of signals received through receive antennas into abaseband signal. The processor 21 decodes and demodulates the radiosignals received through the receive antennas and restores data that theBS 10 originally desired to transmit to the UE. The processor 21 maycontrol the RF unit 23 so that the PUSCH scheduled in the scheduling CCor the scheduled CC by the UL grant through the scheduling CC may betransmitted to the BS 10 through a corresponding CC in a UL SFassociated with the UL grant timing configured/determined according toone method of the present invention. The processor 21 may control the RFunit 23 so that the PHICH for the PUSCH may be received from the BSthrough the scheduling CC in the PHICH timing configured/determinedaccording to one method of the present invention.

The RF units 13 and 23 include one or more antennas. An antenna performsa function for transmitting signals processed by the RF units 13 and 23to the exterior or receiving radio signals from the exterior to transferthe radio signals to the RF units 13 and 23. The antenna may also becalled an antenna port. Each antenna may correspond to one physicalantenna or may be configured by a combination of more than one physicalantenna element. A signal transmitted through each antenna cannot bedecomposed by the UE 20. A Reference Signal (RS) transmitted incorrespondence to a corresponding antenna defines an antenna viewed fromthe UE 20 and enables the UE 20 to perform channel estimation for theantenna, irrespective of whether a channel is a single radio channelfrom one physical channel or a composite channel from a plurality ofphysical antennas including the antenna. That is, an antenna is definedsuch that a channel for transmitting a symbol on the antenna can bederived from the channel through which another symbol on the sameantenna is transmitted. An RF unit supporting a Multi-Input Multi-Output(MIMO) function of transmitting and receiving data using a plurality ofantennas may be connected to two or more antennas.

The detailed description of the preferred embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to exemplary embodiments, those skilled in the art willappreciate that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

[Industrial Applicability]

The present invention is applicable to a BS, a UE, or other equipment ina wireless communication system.

The invention claimed is:
 1. A method for receiving ACKnowledgement(ACK)/Negative ACK (NACK) information from a base station at a userequipment in which a plurality of cells is configured, comprising:transmitting uplink data channel to the base station in an uplink (UL)subframe U₂ of a second cell among the plurality of cells; and receivinga downlink (DL) ACK/NACK channel carrying an ACK/NACK for the UL datachannel from the base station in a DL subframe D₁ of a first cell amongthe plurality of cells; wherein the first cell and the second cell havedifferent Time Division Duplex (TDD) DL-UL configurations, the DLsubframe D₁ is a subframe configured for transmission of a DL ACK/NACKchannel for a UL subframe U₁ of the first cell (where D₁, U₁, and U₂ arenon-negative integers), and the UL subframe U₁ is a first UL subframeamong the UL subframe U₂ and UL subframes on the first cell after the ULsubframe U₂.
 2. The method according to claim 1, wherein the UL subframeU₁ of the first cell is a first UL subframe among subframes after the ULsubframe U₂ of the second cell when a subframe of the first cellcorresponding to the UL subframe U₂ of the second cell operates as DL,and the UL subframe U₁ of the first cell is a subframe sharing a sametime resource as the UL subframe U₂ when the subframe of the first cellcorresponding to the UL subframe U₂ of the second cell operates as UL.3. The method according to claim 1, further comprising: receiving DLACK/NACK channels for N UL subframes of the second cell from the basestation in DL subframes of the first cell, configured for transmissionof DL ACK/NACK channels for first M UL subframes of the first cell amongthe UL subframe U₂ and subframes after the UL subframe U₂, wherein M andN are positive integers, and N is the number of consecutive UL subframesof the second cell, and M≦N.
 4. A method for transmittingACKnowledgement (ACK)/Negative ACK (NACK) information at a base stationto a user equipment in which a plurality of cells is configured,comprising: receiving uplink data channel from the user equipment in anuplink (UL) subframe U₂ of a second cell among the plurality of cells;and transmitting a downlink (DL) ACK/NACK channel carrying an ACK/NACKfor the UL data channel to the user equipment in a DL subframe D₁ of afirst cell among the plurality of cells; wherein the first cell and thesecond cell have different Time Division Duplex (TDD) DL-ULconfigurations, the DL subframe D₁ is a subframe configured fortransmission of a DL ACK/NACK channel for a UL subframe U₁ of the firstcell (where D₁, U₁, and U₂ are non-negative integers), and the ULsubframe U₁ is a first UL subframe among the UL subframe U₂ and ULsubframes on the first cell after the UL subframe U₂.
 5. The methodaccording to claim 4, wherein the UL subframe U₁ of the first cell is afirst UL subframe among subframes after the UL subframe U₂ of the secondcell when a subframe of the first cell corresponding to the UL subframeU₂ of the second cell serves as DL, and the UL subframe U₁ of the firstcell is a subframe sharing a same time resource as the UL subframe U₂when the subframe of the first cell corresponding to the UL subframe U₂of the second cell operates as UL.
 6. The method according to claim 4,further comprising: transmitting DL ACK/NACK channels for N UL subframesof the second cell to the user equipment in DL subframes of the firstcell, configured for transmission of DL ACK/NACK channels for first M ULsubframes of the first cell among the UL subframe U₂ and subframes afterthe UL subframe U₂, wherein M and N are positive integers, and N is thenumber of consecutive UL subframes of the second cell, and M≦N.
 7. Auser equipment, in which a plurality of cells is configured, forreceiving ACKnowledgement (ACK)/Negative ACK (NACK) information from abase station, comprising: a Radio Frequency (RF) unit configured totransmit and receive a radio signal; and a processor configured tocontrol the RF unit, wherein the processor controls the RF unit totransmit uplink data channel to the base station in an uplink (UL)subframe U₂ of a second cell among the plurality of cells and controlsthe RF unit to receive a downlink (DL) ACK/NACK channel carrying anACK/NACK for the UL data channel from the base station in a DL subframeD₁ of a first cell among the plurality of cells, and wherein the firstcell and the second cell have different Time Division Duplex (TDD) DL-ULconfigurations, the DL subframe D₁ is a subframe configured fortransmission of a DL ACK/NACK channel for a UL subframe U₁ of the firstcell (where D₁, U₁, and U₂ are non-negative integers), and the ULsubframe U₁ is a first UL subframe among the UL subframe U₂ and ULsubframes on the first cell after the UL subframe U₂.
 8. The userequipment according to claim 7, wherein the UL subframe U_(i) of thefirst cell is a first UL subframe among subframes after the UL subframeU₂ of the second cell when a subframe of the first cell corresponding tothe UL subframe U₂ of the second cell operates as DL, and the ULsubframe U₁ of the first cell is a subframe sharing a same time resourceas the UL subframe U₂ when the subframe of the first cell correspondingto the UL subframe U₂ of the second cell operates as UL.
 9. The userequipment according to claim 7, wherein the processor controls the RFunit to receive DL ACK/NACK channels for N UL subframes of the secondcell from the base station in DL subframes of the first cell, configuredfor transmission of DL ACK/NACK channels for first M UL subframes of thefirst cell among the UL subframe U₂ and subframes after the UL subframeU₂, and wherein M and N are positive integers, and N is the number ofconsecutive UL subframes of the second cell, and M≦N.
 10. A base stationfor transmitting ACKnowledgement (ACK)/Negative ACK (NACK) informationto a user equipment in which a plurality of cells is configured,comprising: a Radio Frequency (RF) unit configured to transmit andreceive a radio signal; and a processor configured to control the RFunit, wherein the processor controls the RF unit to receive uplink datachannel from the user equipment in an uplink (UL) subframe U₂ of asecond cell among the plurality of cells and controls the RF unit totransmit a downlink (DL) ACK/NACK channel carrying an ACK/NACK for theUL data channel to the user equipment in a DL subframe D₁ of a firstcell among the plurality of cells, wherein the first cell and the secondcell have different Time Division Duplex (TDD) DL-UL configurations, theDL subframe D₁ is a subframe configured for transmission of a DLACK/NACK channel for a UL subframe U₁ of the first cell (where D₁, U₁,and U₂ are non-negative integers), and the UL subframe U₁ is a first ULsubframe among the UL subframe U₂ and UL subframes on the first cellafter the UL subframe U₂.
 11. The base station according to claim 10,wherein the UL subframe U₁ of the first cell is a first UL subframeamong subframes after the UL subframe U₂ of the second cell when asubframe of the first cell corresponding to the UL subframe U₂ of thesecond cell operates as DL, and the UL subframe U₁ of the first cell isa subframe sharing the same time resource as the UL subframe U₂ when thesubframe of the first cell corresponding to the UL subframe U₂ of thesecond cell operates as UL.
 12. The base station according to claim 10,wherein the processor controls the RF unit to transmit DL ACK/NACKchannels for N UL subframes of the second cell to the user equipment inDL subframes of the first cell, configured for transmission of DLACK/NACK channels for first M UL subframes of the first cell among theUL subframe U₂ and subframes after the UL subframe U₂, and wherein M andN are positive integers, N is the number of consecutive UL subframes ofthe second cell, and M≦N.